/**
 *   Byte-oriented AES-256 implementation.
 *   All lookup tables replaced with 'on the fly' calculations.
 *
 *   Copyright (c) 2007-2009 Ilya O. Levin, http://www.literatecode.com
 *   Other contributors: Hal Finney
 *
 *   Permission to use, copy, modify, and distribute this software for any
 *   purpose with or without fee is hereby granted, provided that the above
 *   copyright notice and this permission notice appear in all copies.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 *   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 *   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 *   ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 *   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 *   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 *   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "aes256_cbc.h"

#include <stdint.h>
#include <string.h> // CBC mode, for memset
namespace aes256_cbc {

#define Nb 4
#define Nk 8
#define Nr 14




/*****************************************************************************/
/* Private variables:                                                        */
/*****************************************************************************/
// state - array holding the intermediate results during decryption.
    typedef uint8_t state_t[4][4];


// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM -
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
    static const uint8_t sbox[256] = {
            //0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F
            0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
            0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
            0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
            0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
            0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
            0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
            0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
            0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
            0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
            0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
            0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
            0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
            0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
            0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
            0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
            0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16};

    static const uint8_t rsbox[256] = {
            0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
            0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
            0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
            0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
            0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
            0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
            0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
            0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
            0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
            0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
            0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
            0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
            0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
            0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
            0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
            0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d};

// The round constant word array, Rcon[i], contains the values given by
// x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
    static const uint8_t Rcon[11] = {
            0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};


#define getSBoxValue(num) (sbox[(num)])

#define getSBoxInvert(num) (rsbox[(num)])


// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
    static void KeyExpansion(uint8_t *RoundKey, const uint8_t *Key) {
        unsigned i, j, k;
        uint8_t tempa[4]; // Used for the column/row operations

        // The first round key is the key itself.
        for (i = 0; i < Nk; ++i) {
            RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
            RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
            RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
            RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
        }

        // All other round keys are found from the previous round keys.
        for (i = Nk; i < Nb * (Nr + 1); ++i) {
            {
                k = (i - 1) * 4;
                tempa[0] = RoundKey[k + 0];
                tempa[1] = RoundKey[k + 1];
                tempa[2] = RoundKey[k + 2];
                tempa[3] = RoundKey[k + 3];

            }

            if (i % Nk == 0) {
                // This function shifts the 4 bytes in a word to the left once.
                // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]

                // Function RotWord()
                {
                    k = tempa[0];
                    tempa[0] = tempa[1];
                    tempa[1] = tempa[2];
                    tempa[2] = tempa[3];
                    tempa[3] = k;
                }

                // SubWord() is a function that takes a four-byte input word and
                // applies the S-box to each of the four bytes to produce an output word.

                // Function Subword()
                {
                    tempa[0] = getSBoxValue(tempa[0]);
                    tempa[1] = getSBoxValue(tempa[1]);
                    tempa[2] = getSBoxValue(tempa[2]);
                    tempa[3] = getSBoxValue(tempa[3]);
                }

                tempa[0] = tempa[0] ^ Rcon[i / Nk];
            }

            if (i % Nk == 4) {
                // Function Subword()
                {
                    tempa[0] = getSBoxValue(tempa[0]);
                    tempa[1] = getSBoxValue(tempa[1]);
                    tempa[2] = getSBoxValue(tempa[2]);
                    tempa[3] = getSBoxValue(tempa[3]);
                }
            }

            j = i * 4;
            k = (i - Nk) * 4;
            RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
            RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
            RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
            RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
        }
    }


    void AES_init_ctx(struct AES_ctx *ctx, const uint8_t *key) {
        KeyExpansion(ctx->RoundKey, key);
    }

    void AES_init_ctx_iv(struct AES_ctx *ctx, const uint8_t *key, const uint8_t *iv) {
        KeyExpansion(ctx->RoundKey, key);
        memcpy(ctx->Iv, iv, AES_BLOCKLEN);
    }

    void AES_ctx_set_iv(struct AES_ctx *ctx, const uint8_t *iv) {
        memcpy(ctx->Iv, iv, AES_BLOCKLEN);
    }


// This function adds the round key to state.
// The round key is added to the state by an XOR function.
    static void AddRoundKey(uint8_t round, state_t *state, uint8_t *RoundKey) {
        uint8_t i, j;
        for (i = 0; i < 4; ++i) {
            for (j = 0; j < 4; ++j) {
                (*state)[i][j] ^= RoundKey[(round * Nb * 4) + (i * Nb) + j];
            }
        }
    }

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
    static void SubBytes(state_t *state) {
        uint8_t i, j;
        for (i = 0; i < 4; ++i) {
            for (j = 0; j < 4; ++j) {
                (*state)[j][i] = getSBoxValue((*state)[j][i]);
            }
        }
    }

// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
    static void ShiftRows(state_t *state) {
        uint8_t temp;

        // Rotate first row 1 columns to left
        temp = (*state)[0][1];
        (*state)[0][1] = (*state)[1][1];
        (*state)[1][1] = (*state)[2][1];
        (*state)[2][1] = (*state)[3][1];
        (*state)[3][1] = temp;

        // Rotate second row 2 columns to left
        temp = (*state)[0][2];
        (*state)[0][2] = (*state)[2][2];
        (*state)[2][2] = temp;

        temp = (*state)[1][2];
        (*state)[1][2] = (*state)[3][2];
        (*state)[3][2] = temp;

        // Rotate third row 3 columns to left
        temp = (*state)[0][3];
        (*state)[0][3] = (*state)[3][3];
        (*state)[3][3] = (*state)[2][3];
        (*state)[2][3] = (*state)[1][3];
        (*state)[1][3] = temp;
    }

    static uint8_t xtime(uint8_t x) {
        return ((x << 1) ^ (((x >> 7) & 1) * 0x1b));
    }

// MixColumns function mixes the columns of the state matrix
    static void MixColumns(state_t *state) {
        uint8_t i;
        uint8_t Tmp, Tm, t;
        for (i = 0; i < 4; ++i) {
            t = (*state)[i][0];
            Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3];
            Tm = (*state)[i][0] ^ (*state)[i][1];
            Tm = xtime(Tm);
            (*state)[i][0] ^= Tm ^ Tmp;
            Tm = (*state)[i][1] ^ (*state)[i][2];
            Tm = xtime(Tm);
            (*state)[i][1] ^= Tm ^ Tmp;
            Tm = (*state)[i][2] ^ (*state)[i][3];
            Tm = xtime(Tm);
            (*state)[i][2] ^= Tm ^ Tmp;
            Tm = (*state)[i][3] ^ t;
            Tm = xtime(Tm);
            (*state)[i][3] ^= Tm ^ Tmp;
        }
    }

#define Multiply(x, y)                                \
      (  ((y & 1) * x) ^                              \
      ((y>>1 & 1) * xtime(x)) ^                       \
      ((y>>2 & 1) * xtime(xtime(x))) ^                \
      ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^         \
      ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))))   \


// MixColumns function mixes the columns of the state matrix.
// The method used to multiply may be difficult to understand for the inexperienced.
// Please use the references to gain more information.
    static void InvMixColumns(state_t *state) {
        int i;
        uint8_t a, b, c, d;
        for (i = 0; i < 4; ++i) {
            a = (*state)[i][0];
            b = (*state)[i][1];
            c = (*state)[i][2];
            d = (*state)[i][3];

            (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
            (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
            (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
            (*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
        }
    }


// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
    static void InvSubBytes(state_t *state) {
        uint8_t i, j;
        for (i = 0; i < 4; ++i) {
            for (j = 0; j < 4; ++j) {
                (*state)[j][i] = getSBoxInvert((*state)[j][i]);
            }
        }
    }

    static void InvShiftRows(state_t *state) {
        uint8_t temp;

        // Rotate first row 1 columns to right
        temp = (*state)[3][1];
        (*state)[3][1] = (*state)[2][1];
        (*state)[2][1] = (*state)[1][1];
        (*state)[1][1] = (*state)[0][1];
        (*state)[0][1] = temp;

        // Rotate second row 2 columns to right
        temp = (*state)[0][2];
        (*state)[0][2] = (*state)[2][2];
        (*state)[2][2] = temp;

        temp = (*state)[1][2];
        (*state)[1][2] = (*state)[3][2];
        (*state)[3][2] = temp;

        // Rotate third row 3 columns to right
        temp = (*state)[0][3];
        (*state)[0][3] = (*state)[1][3];
        (*state)[1][3] = (*state)[2][3];
        (*state)[2][3] = (*state)[3][3];
        (*state)[3][3] = temp;
    }


// Cipher is the main function that encrypts the PlainText.
    static void Cipher(state_t *state, uint8_t *RoundKey) {
        uint8_t round = 0;

        // Add the First round key to the state before starting the rounds.
        AddRoundKey(0, state, RoundKey);

        // There will be Nr rounds.
        // The first Nr-1 rounds are identical.
        // These Nr-1 rounds are executed in the loop below.
        for (round = 1; round < Nr; ++round) {
            SubBytes(state);
            ShiftRows(state);
            MixColumns(state);
            AddRoundKey(round, state, RoundKey);
        }

        // The last round is given below.
        // The MixColumns function is not here in the last round.
        SubBytes(state);
        ShiftRows(state);
        AddRoundKey(Nr, state, RoundKey);
    }

    static void InvCipher(state_t *state, uint8_t *RoundKey) {
        uint8_t round = 0;

        // Add the First round key to the state before starting the rounds.
        AddRoundKey(Nr, state, RoundKey);

        // There will be Nr rounds.
        // The first Nr-1 rounds are identical.
        // These Nr-1 rounds are executed in the loop below.
        for (round = (Nr - 1); round > 0; --round) {
            InvShiftRows(state);
            InvSubBytes(state);
            AddRoundKey(round, state, RoundKey);
            InvMixColumns(state);
        }

        // The last round is given below.
        // The MixColumns function is not here in the last round.
        InvShiftRows(state);
        InvSubBytes(state);
        AddRoundKey(0, state, RoundKey);
    }


    static void XorWithIv(uint8_t *buf, uint8_t *Iv) {
        uint8_t i;
        for (i = 0; i < AES_BLOCKLEN; ++i) // The block in AES is always 128bit no matter the key size
        {
            buf[i] ^= Iv[i];
        }
    }

    void AES_CBC_encrypt_buffer(struct AES_ctx *ctx, uint8_t *buf, uint32_t length) {
        uintptr_t i;
        uint8_t *Iv = ctx->Iv;
        for (i = 0; i < length; i += AES_BLOCKLEN) {
            XorWithIv(buf, Iv);
            Cipher((state_t *) buf, ctx->RoundKey);
            Iv = buf;
            buf += AES_BLOCKLEN;
            //printf("Step %d - %d", i/16, i);
        }
        /* store Iv in ctx for next call */
        memcpy(ctx->Iv, Iv, AES_BLOCKLEN);
    }

    void AES_CBC_decrypt_buffer(struct AES_ctx *ctx, uint8_t *buf, uint32_t length) {
        uintptr_t i;
        uint8_t storeNextIv[AES_BLOCKLEN];
        for (i = 0; i < length; i += AES_BLOCKLEN) {
            memcpy(storeNextIv, buf, AES_BLOCKLEN);
            InvCipher((state_t *) buf, ctx->RoundKey);
            XorWithIv(buf, ctx->Iv);
            memcpy(ctx->Iv, storeNextIv, AES_BLOCKLEN);
            buf += AES_BLOCKLEN;
        }

    }

}